The pediatric surgeon was with his wife for a weekend getaway when he spotted two children struggling in Lake Michigan off a small beach in Berrien County Michigan Sunday morning. Liu was able to help the children but was pulled under the water and drowned, according to authorities and his friends.

"Dr. Liu drowned while successfully saving two children who got caught in heavy surf in Lake Michigan," said his friend and colleague, Dr. Jeffrey Matthews, chairman of surgery at the University of Chicago Hospitals, where Liu practiced.

"He managed to help them but he got pulled down by the undertow himself," Matthews said. "He really died a hero."

Liu had recently celebrated his 50th birthday and was spending the weekend with his wife and three small children in Chikaming Township, about 90 miles from Chicago. Around 9:40 a.m., he saw the children in trouble off Cherry Beach, police said.

Liu went out to help and went under the water before rescue crews arrived, according to Jeff Thornton, a dispatch supervisor for Berrien County Public Safety. "He was a responder who went out to help," Thornton said, but he had no details.

Thornton said Liu's death was one of two apparent drownings in the county Sunday. A 41-year-old man from west suburban Montgomery drowned a few hours later in the lake.

The unidentified victim from Montgomery was located in 12 feet of water in a rip current 350 yards off Tiscornia Beach in St. Joseph, according to a statement released by St. Joseph City Public Safety. He was pulled from the waters byU.S. Coast Guardworkers and taken to Lakeland Hospital, where he was pronounced dead, the statement said.

He was last seen in waves that were 6-8 feet high.

“It looks like he got caught in the rip,’’ said Thornton of the Montgomery man. “The rip current is just a huge undertow caused by large waves that causes suction,’” Thorton said.

The rip current could also have played a role in the doctor’s death, said Thornton.

“It could very well have resulted in the same thing,’’ Thornton said.

Liu lived in Hyde Park and had worked at the hospital for about 10 years. He had recently been awarded a "distinguished clinician" award at the hospital.

"It’s incredibly sad," said Matthews. "We are so absolutely heartbroken by the loss of our friend and colleague. Ironically, he died saving children which is what he does every day.

"He was a brilliant, caring, compassionate surgeon and one of the most wonderful people you would ever meet," Matthews said. "He was beloved in the Hyde Park community and he’s just a prince of a man.

"He was a remarkable human being. We are all shocked," Matthews continued. “He was very passionate about his work. What the children needed was what always what he talked about. He was a world-class pediatric surgeon who made innovations and advancements in minimally invasive surgery for children and cared for trauma victims."

Another friend, Dr. John Cunningham, a pediatric oncologist at the University of Chicago Hospitals, said he knew Liu for six years and regarded him as "a brilliant surgeon."

"It wasn’t just his clinical skills, but his people skills were just magnificent,’’ Cunningham said. “He was a stellar communicator to families and children when they were facing very, very difficult challenges.’’

He was also known for his teaching, training the “next generation of Chinese surgeons, because of his heritage’’ said Cunningham.

“He lit up the room. He was a gregarious person who, when he spoke about a topic, you really felt that something good would happen,’’ Cunningham said. "I spoke with him on Tuesday and he was his usual happy and wonderful self.’’

Liu joined the University of Chicago Hospitals as a pediatric surgeon in 2001, and was named section chief of pediatric surgery and surgeon-in-chief at Comer Children’s Hospital in 2007. He is survived by his wife, Dr. Dana Suskind, and three children: Genevieve, 13, Asher, 10, and Amalie, 7.